(1) Field of the Invention
The present invention relates to an improvement in an optical transmission member-fixed assembly comprising a substrate and a lid integrated with the substrate, the substrate being provided with a receipt groove for receiving a core wire of an optical fiber and a receipt seat for receiving at least a covering for the optical fiber.
(2) Related Art Statement
Various types of substrates are known to fix optical fibers having diameters of, for example, around 125 .mu.m. In these substrates, if the optical axis of an optical fiber fixed onto the substrate deviates from a given location, a light transmission loss between the optical fiber and another optical transmission means increases. Therefore, an extremely high working precision such as 0.5 .mu.m or less is required in a fixing groove of the optical fiber-fixing substrate. In such a substrate, grooves each having a V-shaped section are formed in the substrate, each optical fiber is placed in the corresponding groove, and each optical fiber is fixed there with a resin or solder.
FIG. 1(a) is a front view for schematically illustrating an example of an optical fiber-fixed assembly with such an optical fiber-fixing substrate, and FIGS. 1(b) and 1(c) are a plane view and a left side view for also schematically illustrating this assembly, respectively. The optical fiber-fixed assembly 1 includes a fixing substrate 3 and lids 2 and 4. The fixing substrate 3 includes a receipt seat 3c for receiving optical fibers, covering 5 A lid 2 is placed on the coverings 5. A holding portion 3a of the fixing substrate 3 is provided with given rows of receipt grooves 9. Each groove 9 extends from an end face 7 toward a stepped portion 3b. A core wire 8 of the optical fiber is placed in each groove 9, and fixed there with an adhesive such as a resin. The lid 4 is placed on the holding portion 3a.
Below will be described a process for producing such an optical fiber-fixed assembly. First, an optical fiber-fixing substrate is prepared from ceramic or glass. Each receipt groove 9 is as, thin as, for example, one hundred to dozens of microns. A core wire 8 of an optical fiber is inserted in each groove 9.
However, the present inventors discovered that the above optical fiber-fixed assembly might suffer from the following problems. That is, the fixed assembly is desired to suppress the insertion loss of the light to a given area over a wide temperature range. The optical fiber-fixed assembly is often arranged in a very low temperature environment. Alternatively, if the optical fiber-fixed assembly is arranged in an automobile, it may reach a temperature of 85.degree. C. even in the shade depending upon the location of the automobile.
More specifically, the operational temperature environment of optical parts mounted in automobiles is classified into the following three cases. That is, if the optical part is mounted in the trunk space, the optical part needs to withstand temperature changes in a range of -20.degree. C. to +60.degree. C. If it is mounted in the vehicle compartment into which sun light does not directly enter, it needs to withstand temperature changes in a range of -40.degree. C. to +85.degree. C. lastly, when the optical part is mounted in the engine compartment, it needs to withstand temperature changes in a range of -40.degree. C. to +120.degree. C.
Accordingly, the present inventors produced optical-fiber fixed assemblies each having a configuration as shown in FIGS. 1(a) to 1(c), placed each of them in a given package and then subjected the package to a heat impact test and a heat cycle test over a wide temperature range of for example -40.degree. C. to +85.degree. C. As a result, it was revealed that defective packages having their light insertion loss remarkably reduced might occur after the heat impact test or the heat cycle test, which might cause reduction in yield.